This disclosure relates to cooling holes for gas turbine engine components, such as airfoils. More particularly, the disclosure relates to the exit geometry of the cooling hole on the exterior surface of the component.
Gas turbine engines typically employ stator vanes and rotor blades that have internal cooling passages in airfoil and/or platform. Some internal cooling passages fluidly communicate with cooling holes that exit at the exterior surface of the airfoil and/or platform. Other gas turbine engine components also may incorporate such cooling passages and holes.
Typically, cylindrical cooling holes are provided, which may be machined using a variety of techniques, such as a round, cylindrically shaped electrical discharge machining (EDM) electrode. When the cylindrical holes are drilled into the blade or vane, an elliptical footprint or exit area is provided on the exterior surface of the airfoil. The holes may be susceptible to cracking from thermal mechanical fatigue. The cracks of one hole may propagate and join with cracks of an adjacent hole, which may result in a component that is not suitable for continued used.